OPTOKINETIC AND OTHER FACTORS MODIFYING VESTIBULAR NYSTAGMUS

Abstract

IT HAS been common practice clinically to concentrate attention in ophthalmologic diagnosis on the two separate entities of "ocular" and "central" nystagmus. In so doing, optokinetic nystagmus has been relegated to a group of interesting phenomena which have little application in practice. The purpose of this paper is to present the accumulated knowledge regarding the modifying effect of optokinetic nystagmus and to add further experimental data. Optokinetic nystagmus has been typified in ophthalmologic literature by the term "railroad nystagmus." When a subject allows his gaze to follow a moving object in the passing landscape, a slow deviation occurs which allows fixation to be maintained on the object. When an end position is reached beyond which head movement would be required for further fixation, a quick return to the primary position occurs, and the cycle is repeated as long as attention is maintained. The slow and quick components of the nystagmus